Machine gun gas actuating and evacuation system

ABSTRACT

In a machine gun having a gas-actuating system including a gas cylinder responsive to gas pressure generated by the discharge of a round and including a receiver and a barrel mounted therein having a predetermined bore and a muzzle, a novel gas evacuation means, a novel barrel extension means and a novel gas seal means all for removing exhausted gas from the area surrounding the machine gun receiver, gas cylinder and receiver. The novel gas evacuation means, mounted on the gas cylinder and along the barrel, is in communication with the gas-actuating system for removing exhausted gas therefrom and conveying said exhausted gas for discharge at a location remote from the muzzle; the novel barrel extension is attached to the muzzle of the barrel, has a bore greater than the barrel bore for removing exhausted gas from the muzzle and conveying said exhausted gas for discharge at a location remote therefrom free from interference with the operation of the gun mechanism; and the novel gas seal means includes an obturating nut and sealing collar provided in the gas-actuating system for preventing exhausted gas from passing rearwardly therethrough and escaping from the receiver.

United States Patent 1 91 Folley et al.

[ Feb. 13, 1973 [54] MACHINE GUN GAS ACTUATING AND EVACUATION SYSTEM [75] Inventors: Cranston Wesley Folley, Kennebunk, Maine; John Gonsalves Rocha, Westfield, Mass. [57] ABSTRACT In a machine gun having a gas-actuating system in- [73] Asslgnee' m Corporatlon Chlcago cluding a gas cylinder responsive to gas pressure generated by the discharge of a round and including a [22] Filed: Feb. 12, 1970 receiver and a barrel mounted therein having a [21] Appl.No.: 10,927

Primary Examiner-Stephen C. Bentley Attorney-Martin Kirkpatrick predetermined bore and a muzzle, a novel gas evacuation means, a novel barrel extension means and a novel gas seal means allsfor removing exhausted gas [52] U.S. Cl ..89/193, 89/1 E, 89/14 B, m the area Surrounding the machine g receiver, 89/40 3 gas cylinder and receiver. The novel gas evacuation [51] int.- Cl. ..F41d 5/10, F4lh 7/12 a mounted on the g cylinder and along the [58] Field of Search ..89/l E, 14 R, 16, 191, 192, barrel, is in communication with the gas-actuating 39/193 system for removing exhausted gas therefrom and conveying said exhausted gas for discharge at a location 5 References Cited remote from the muzzle; the novel barrel extension is attached to the muzzle of the barrel, has a bore UNITED STATES PATENTS greater than the barrel bore for removing exhausted 1 388 856 8/1921 Fox ..89/193 x gas f the muzzle i conveying Said exhausted gas 7/937 X for discharge at a location remote therefrom free from 2,1 M69 5/1938 Lauf "89,193 interference with the operation of the gun mechanism; 2,813,735 1/1953 Mamard 39/193 and the novel gas seal means includes an obturating 2,052,368 8/1936 Sutter et 89/193 nut and sealing collar provided in the gas-actuating 3,156,992 1 1/1964 Beretta 89/193 system for preventing exhausted gas from passing rear- 8,257 3 193 wardly therethrough and escaping from the receiver. 1,738,501 12/1929 Moore ...89/193 3,420,140 1/1969 Beretta ..89/ 193 5 Claims, 15 Drawing Figures PATENTEU FEB 1 3 I975 SHEET 10F 4 PATENTED 3573 3,715,955

SHEET 3 OF 4 MACHINE GUN GAS ACTUATING AND EVACUATION SYSTEM This invention relates to gas-operated machine guns and more particularly to improvements in such guns which enable their use in confined spaces, for example, in armored vehicles, aircraft and the like.

The energy of the 'gas generated by the discharge of rounds in a machine gun is widely used to activate those mechanisms which feed, fire and eject the rounds. Such machine guns are preferred over those in which the recoil energy produced by the barrel is utilized for such purposes because the recoil action transferred to the gun support or operator is much less violent. Nevertheless, heretofore, such guns could not be used in confined spaces, such as in armored vehicles and aircraft, because of the noxious gases which are vented from their gas systems during firing operation.

Accordingly, it is a major object of the present invention to provide a gas-operated machine gun which may be successfully operated from within confined spaces.

It is still another object of the present invention to provide novel barrel extensions without affecting gun operatingcharacteristics.

It is yet another object of the invention to reduce fouling by combustion residues of the gas-operating rod guide tube of gas-operated machine guns.

It is another object of the invention to provide mechanisms for modifying presently-existing gasoperated machine guns to make possible the incorporation of the inventions therein.

The above objects are accomplished by providing, in a machine gun of the type having a barrel and a gas-actuating system responsive to gas pressure generated by the discharge of a round in the barrel and in which the actuating system includes a gas cylinder and actuating piston in communication with the barrel, gas evacuation means connected to the cylinder and removing and collecting exhausted gas therefrom and conveying such exhausted gas for discharge at a location remote from the cylinder, which location may be at least as far forward as adjacent the nuz'zle of the barrel. Preferably, novel gas seal means are provided, not only in order to achieve the above stated objects, as to gas evacuation, but also greatly to reduce buildup of combustion residues in the gas-operating rod guide tube. In addition, for incorporation if desired, the invention provides novel barrel extension means having an enlarged bore for substantially extending the barrel length without significantly affecting the operating of characteristics of the gun.

For the purpose of more fully explaining the above and still further objects and features of the invention, reference is now made to the following detailed description of a preferred embodiment thereof, together with the accompanying drawings, wherein:

FIG. 1 is an overall view of a first modification of a gas-operated machine gun according to the present invention adapted for remote operation from within a confined space shown as a tank turret;

FIG. 2 is a side view of a portion of the gun of FIG. 1 especially useful for modifying a presently-existing gasoperated machine gun;

FIGS. 3 and 4 are enlarged side views, partly in section of a portion of the mechanism of FIG. 2, with the gas evacuation mechanism revolved to a position below the gas cylinder mechanism for clarity, showing two different positions of the operating element thereof;

FIG. 5 is an enlarged top view, partly in section, of a portion of the mechanism of FIG. 2, showing the true relationship of gas evacuation assembly to the machine gun barrel;

FIGS. 6 through 9 are transverse sectional views of the mechanism of FIG. 5;

FIGS. 10 through 12 are isometric detail views of portions of the mechanism of FIGS. 2 through 4;

FIG. 13 is an overall view of a second modification of a gas-operated machine gun according to the present invention adapted for manual operation by personnel firing from within a confined space;

FIG. 14 is a side view of a portion of the gun of FIG. 13 especially useful for modifying a presently-existing gas-operated machine gun, and

FIG. 15 is a side view, partly in section, of a portion H of the gun of FIG. 13.

Referring generally to the drawings, the invention is shown as incorporated in a 7.62-MM, M60 machine gun, a widely used gas-operated automatic weapon. Tests have established that the mechanisms of the invention do not adversely affect gun performance. Since the M60 machine gun is well known, the descriptions thereof will be limited herein to such of its mechanism as are related to the present invention.

In the drawings are shown two modifications of an M60 machine gun embodying the present inventions. The first, as shown in FIGS. 1 through 12, especially adapted for use such as in the turret of a tank where an extended length is required, utilizes, in addition to the novel gas evacuation tube and gas seal of the invention, a novel barrel extension. This uniquely makes possible the normal operation of the gas-operated mechanisms of the gun as would not be the case if the barrel were merely made longer, for reasons well known to those skilled in the art.

The second modification omits such barrel extension, and is especially useful as a personal weapon to be carried by an individual soldier.

In each modification, the M60 machine gun on which it is based includes a barrel having a bore of predetermined diameter mounted on a receiver which has an actuating rod for operating those mechanisms which feed, fire and eject the rounds and are conventional to the M60 machine gun.

Thus, referring to said first modification in FIGS. 1 through 12 is shown a machine gun mounted in a tank turret by any suitable means, having a barrel 16 removably mounted on the front end of receiver 24 which has an actuating rod 45.

The mechanism of the present invention in its first preferred embodiment, as best fully shown in FIG. 2, directly replaces the conventional M60 barrel and associated gas cylinder and is adapted to operate the conventional actuating rod 45 thereof. Thus, in FIG. 2 is shown barrel 16 with the conventional bore and the M60 receiver mounting structure 18 at its rear end. A gas cylinder 30 is mounted beneath barrel 16 for operating actuating rod 45, as hereinafter more fully described. Barrel 16 is provided with a novel barrel extension 26 hereinafter more fully described, preferably having a flash suppressor 20. A gas evacuator tube assembly 60 is mounted beneath barrel extension 26 and along the side of barrel 16 for cooperation with gas cylinder 30, as hereinafter more fully explained, for removing exhausted gas therefrom and conveying such exhausted gas for discharge adjacent to the muzzle of barrel extension 26 and flash suppressor 20.

FIGS. 3 and 4, together with their associated FIGS. 5

through 12, show in specific detail the mechanism of,

supply gas energy to the gas cylinder assembly described hereinafter. The forward portion of barrel 16, being tapered toward the barrel muzzle, extends forwardly from receiver 24, having front section 25 of reduced outer diameter.

Barrel extension 26 is mounted on front section 25 (see FIG. 2), has an integral flash suppressor and is provided with a mating sleeve 23 for receiving front section 25 of barrel 16 being secured thereto by threading. Uniquely, to avoid interference with the conventional operation of the M60 mechanism, it is provided with a bore 19 enlarged at least about 2 to 2 h times with respect to barrel bore 29, both to avoid interference with the passage of a bullet therethrough and to avoid changing the gas operation characteristics of the M60 mechanism. Having an overall length of approximately 15.5 inches, barrel extension 26 is especially adaptedfor installation in an M60Al tank for carrying the muzzle blast to the outside of the tank.

As shown in FIGS. 2, 3 and 4, the gas cylinder assembly including a gas cylinder 30 having a cooperating piston is fixedly mounted on barrel 16 approximately midway the length thereof so as to be disposed adjacent the front end of receiver 24. Gas cylinder 30 is supported beneath barrel 16 by mounting brackets 21 and 22, formed integrally with gas cylinder 30, each being pinned to barrel 16 for secure attachment thereto. A conventional gas cylinder extension 36 having a relief hole 37 is threaded into the forward end of the gas cylinder 30, being locked by lock washer 38. Disposed within the opposite end of gas cylinder 30 (see FIG. 15) is the forward end 34 of actuating rod 45,

of conventional construction extending forwardly from its surrounding operating tube 39 included in receiver 24, for operating those mechanisms which feed, fire and eject rounds of ammunition and are conventional to the M60 machine gun.

In order to prevent leakage of gas from the receiver end of tube 39 and also to prevent leakage into said tube for preventing the build-up of combustion residues therein and in the receiver 24 which might affect gun operation, novel sealing means are provided according to the invention. These means include two seal members, obturating nut 31, being stationary, and sealing collar 35, being movable, constructed to provide dual sealing during firing and effective to prevent leakage of gas both outwardly to the surrounding atmosphere and rearwardly to receiver 24. Obturating nut 31 is positioned between gas cylinder 30 and operating tube 39, has inner sealing surface 32 provided with three annular grooves and contains shoulder 33.

When in the forward position (see FIG. 15) actuating rod 45 is slideably received within sealing surface 32 such that gases laden with combustion residue are prevented from leaking rearwardly from gas cylinder 30 during the initial firing stage. Sealing collar 35, being of annular construction of outer diameter somewhat less than the surrounding inner diameter of operating tube 39, is fixedly mounted by pinning on shaft 51 of actuating rod 45 adjacent louvered cleaning head 55.

Head 55, of known construction is provided with louvres for reaming combustion residue deposits on the inner surface of tube 39 during reciprocal travel of actuating rod 45 therein. Sealing collar 35 having an outer diameter less than the outer diameter of the louvers and slightly spaced from the inner diameter of operating tube 39 prevents gas leaking past head 55 from entering receiver 24, all without interfering with the function of head 55.

Piston 40, also of conventional construction disposed within cylinder bore 42 of gas cylinder 30, being free to slide reciprocably therein, is provided with six radially extending spaced holes 43, an inner chamber 41, a forward open end and a rear wall 44. With piston 40 occupying the forward portion of gas cylinder 30 (see FIG 15) with the open end adjacent gas cylinder extension 36, the holes 43 are surrounded by annular gas input chamber or part 46 formed in cylinder bore 42. Actuating rod 45 is movable from a forward position shown in FIG. 15 to a rear position wherein end 34 is wholly contained in operating tube 39 and is out of engagement with gas cylinder nut 31 as seenin FIG. 3.

As viewed in FIGS. 7 and 11, a selector valve 52 for regulating the flow of gas from barrel bore 29 to gas cylinder 30 is provided in bracket 22 adjacent barrel port 28 having a valve body 48 formed integrally with the portion of bracket 22 projecting transversely outwardly in a left hand direction. Included in valve body 48 is inlet port 49 in communication with barrel port 28 and annular chamber 47, outlet port 50 in communication with annular chamber 47 and cylinder bore 42, and selector valve 52 having passages 53 and 54 on opposite sides (see FIG. 11), passages53 having relatively greater cross-sectional area than passage 54, pin 56, nut 57, and lock washer 58. By loosening nut 57, pin 56 may be disengaged from a mounting recess in bracket 22 such that selector valve 52 may be rotated through an arc of 180 to place either passage 53 or 54 in communication with inlet port 49 and outlet port 50.

As seen in FIGS. 6 and 10, an elbow bracket formed integrally with the rear portion of gas cylinder 30 extends transversely on the side opposite selector valve 47 at 45 with a vertical plane through the axis of barrel 16 and gas cylinder 30. Elbow bracket 70 includes bore 71 extending rearwardly in a directionparallel with cylinder bore 42 to communicate with or exhaust port exit port 72, extending transversely from bore 71 inwardly to chamber 76 provided at the rear of cylinder bore 42 for directing gas from gas cylinder 30 outwardly to the enclosed gas evacuation assembly 60. Provided on the outer slanting surface 73 of elbow bracket 70 is a tee shaped slot 74.

The gas evacuator assembly 60 seen in FIGS. 2 and 3, being constructed to remove all the noxious gases from the area surrounding the gas cylinder assembly,

and including an evacuator tube 61, a support cap 62 and gas tube 64, extends forwardly from the rear of gas cylinder 30 to a position adjacent and beneath and flash suppressor 20.

As seen in FIG. 16 the rear portion of evacuator tube 61 is provided with a tube lock bracket 78 having a spring lock 80 for locking evacuator tube 61 to gas cylinder 30 in a readily detachable manner. Locking of tube lock bracket 78 to elbow bracket 70 is necessary to prevent evacuator tube 61 from otherwise creeping forward relative to gas cylinder 30 responsive to gas pressure and becoming disengaged therefrom with resulting undesirable gas leakage. In the locked position the distal end of evacuator tube 61, having orifice 83, is slidably'receive'd'in bore 71, with orifice 83 in alignment with exit port 72, tube lock bracket 78 butting elbow bracket 70, and spring lock 80 overlaying slot 74. As seen in FIG. 5, evacuator tube 61 extends forwardly from elbow bracket 70 along the right handsides of barrel 16 and gas cylinder 30, formed to follow the contour of said barrel and gas cylinder to engage support cap 62.

As viewed in FIGS. 3, 8 and 12, support cap 62 mounted on the forward end of gas cylinder extension 36 is provided with a central bore 86 for slideably receiving gas cylinder extension 36, a coaxial socket 88 for securely engaging gas tube 64 by sweating, an outer bone 90 for securely engaging evacuator tube 61 by sweating and a channel 92 extending inwardly from outer bore 99 to coaxial socket 88. The functions served by support cap 62 are to securely attach gas tube 64 to gas evacuator tube 61, to support the gas evacuator assembly 60 on cylinder tube extension 36, to provide a gas passage angles inwardly between said gas tube and evacuator tube and to provide a collection chamber for gases emitted from relief hole 37. The gas tube 64 extends from support cap 62, forwardly beneath barrel 16 to a slanted tip 94 adjacent flash suppressor 20 being securely mounted to barrel 16 by tube clamp 96. Included in tube clamp 96, shown in FIGS. 2 and 9, is a barrel ring 97 surrounding barrel extension 26 mounted in a recess adjacent flame suppressor 20, a tube ring 98 surrounding gas tube 64 adjacent slanted tip 94, and a screw 100. Tube clamp 96 (see especially FIG. 9), is slotted for exerting an outwardly expanding force on screw 100, upon being threaded inwardly, tending to lock said screw in place.

The configuration of the gas evacuator assembly together with the gas cylinder mounting structure as just described is formed in a special compact shape such that an M60 machine gun modified according to the present invention may be fitted into the conventional machine gun installation of an M60Al tank.

Referring to FIG. 2, provision for mounting of the gas tube assembly 60 includes tube clamp 96 securely fastened to barrel extension 26, support cap 62 slideably received by gas cylinder extension 36, spring lock 80 engaging slot 74 and bore 71 receiving the terminal end of evacuator tube 61. Accordingly, removal of the gas tube assembly is readily accomplished by loosening screw 100 of tube clamp 96, unscrewing barrel extension 26 from barrel 16, releasing spring 80 from elbow bracket 70, and sliding the barrel extension 26 and gas tube assembly 60 forwardly to disengage evacuator tube 61 from elbow bracket 70 and support cap 62 from gas cylinder extension tube 36.

In operation, upon firing of the machine gun by actuation of the conventional M60 firing mechanism, hot gas carrying combustion residue enters barrel port 28, after the round projectile has passed thereby, and is directed by selector valve 52 into annular chamber 46. Holes 43 of piston 40, normally being aligned with annular chamber 46, admit gas into piston chamber 41 causing piston 40 and actuating rod 45 to be driven rearwardly in gas cylinder 30 by the expanding hot gas. The force of the expanding hot gas transmitted by piston 40 is sufficient to drive actuating rod 45 from a forward position extending into gas cylinder 30 to a rear position within operating tube 39 wherein end 34 is out of engagement with obturation nut 31 (see FIG. 3). Rearward displacement of actuating rod 45 actuates the M60 breech mechanism in a conventional manner causing extraction and ejection of the case of the fired round, and cocking the bolt.

The gas, being confined within chamber 41, drives piston 40 to the rear of gs cylinder 30 against obturation nut 31 to align holes 43 with chamber 76, to enclose the rear end of gas cylinder 30 and compress rear wall 44 against shoulder 33 effective to seal the forward face of obturating nut 31.

Throughout rearward travel of actuating rod 45 sealing collar 35 continually cooperates with the inner surface of operating tube 39 to prevent such gas as may enter said operating tube through obturation nut 31 from entering receiver 24. Provision of this second gas sealing means therefore results in continuous sealing of leakage paths between gas cylinder 30 and receiver 24 throughout operation of actuating rod 45, even though obturation nut 31 permits some gas leakage into operating tube 39 during a brief interval when end 34 is out of engagement with sealing surface 32. Furthermore, by reducing the exposure of the inner surface of operating tube 39 to gas laden with combustion residue, sealing collar 35 effectively prevents excessive buildup of deposits of said residue, thus avoiding sluggish operation of the feeding and firing mechanism.

When piston 40 is abutting obturation nut 31, holes 43 are in alignment with exhaust chamber 76 permitting gas contained in chamber 41 to pass out of gas cylinder 30, through exit port 72 and into evacuator tube 61. Gas entering evacuator tube 61 passes forwardly sequentially through an enclosed passageway comprising said evacuator tube, channel 92 of support cap 62 and gas tube 64 to be exhausted from slanted tip 94 adjacent flash suppressor 20. Also, gas contained in chamber 41 is free to expand forwardly into gas cylinder extension 36, a small portion of which is permitted to escape through hole 37 acting as a pressure relief orifice into gas tube 64.

The amount of gas entering chamber 41 is regulated by rotating selector valve 47 through an arc of from the normal position to a second position. In the normal position, passage 54 of relatively smaller crosssection is in communication with both inlet port 49 and outlet port 50 to provide a given flow of gas to gas cylinder 30 for normal operation of the gas operating mechanism. At such time as firing of the machine gun becomes sluggish, selector valve 47 can be rotated to align passage 53 of greater cross-section with inlet port 49 and outlet port 50 to provide increased flow of gas to the gas cylinder to increase the firing rate of the gun.

In another embodiment adapted for field use as seen in FIGS. 13, I4 and 15, in lieu of a barrel extension, sight 106 and mount 108, both of conventional M60 construction are mounted on front section 25 of barrel 16 with a convention flash suppressor secured by threads provided in the forward end of barrel 16. The gas tube 110 being correspondingly shorter is supported only by support cap 62.

In a further embodiment of the invention the novel obturating nut 31 and sealing collar 35 are included in a conventional M60 machine gun for the purpose of preventing gas laden with combustion residue from entering operating tube 39 and receiver 24 otherwise resulting in a retarded firing rate.

Various modifications of the invention, within the scope of the invention and the appended claims, will be apparent to those skilled in the art.

What is claimed is:

1. In a machine gun with a barrel having a bore of predetermined diameter with a forward muzzle end and a rearward receiver end having a receiver including mechanism which operates said gun that improvement which consists of:

gas actuating and evacuation means responsive to gas pressure generated by the discharge of a round in said barrel for operating said receiver mechanism and collecting exhausted gas for discharge at a location at least as far forward as adjacent the nuzzle end of said barrel, said means comprising barrel gas port means including a gas port in said bore located generally in the mid-portion of said barrel,

a gas cylinder mounted on said barrel, said cylinder having a forwardly located gas inlet port communicating with said barrel gas port for supplying to said cylinder gas under pressure from said barrel and forwardly and rearwardly located gas outlet ports a piston within said cylinder movable between a forward position in communication with said cylinder gas inlet port to a rearward position in communication with said rearward gas outlet port gas evacuation tube means extending forwardly externally of said cylinder generally parallel thereto and to said barrel from said rearwardly located gas outlet port to a location at least as far forward as adjacent the muzzle end of said barrel said gas evacuation tube means communicating with said forwardly and rearwardly located cylinder gas outlet ports for discharging said exhausted gas in a forward direction at least as far forward as adjacent the muzzle end of said barrel.

2. In a machine gun with a barrel having a bore of predetermined diameter with a forward muzzle end and a rearward receiver end having a receiver including mechanism which operates said gun that improvement which consists of:

gas actuating and evacuation means responsive to gas pressure generated by the discharge of a round in said barrel for operating said receiver mechanism and collecting exhausted gas for discharge in a forward direction, said means comprising:

barrel gas port means including a gas port in said bore located generally in the mid-portion of said barrel a gas cylinder mounted on said barrel, said cylinder having a forwardly located gas inlet port communicating with said barrel gas port for supplying to said cylinder gas under pressure from said barrel and a rearwardly located gas outlet port a piston within said cylinder movable between a forward position in communication with said cylinder gas inlet port to a rearward position in communication with said rearward gas outlet port an operating tube extending between the rear end of said cylinder and said receiver an actuating rod in said tube, said actuating rod extending through the rear wall of said cylinder for actuation by said piston for movement of said rod in said tube independently of said piston to operate said receiver mechanism rod sealing means mounted on said actuating rod and cooperating with said operating tube for preventing exhausted gas from leaking into said receiver and for controlling deposit of said combustion residues within said operating tube and gas evacuation means extending from said rearwardly located cylinder gas outlet port for discharging exhausted gas in a forward direction.

3. In a machine gun as claimed in claim 2, wherein said gas sealing means further includes cylinder sealing means positioned between said cylinder and said actuating rod for restricting the passage of exhausted gas carrying combustion residues into said operating tube.

4. In a machine gun as claimed in claim 3 wherein said gas seal means consists of an obturating nut positioned between said cylinder and said operating rod tube for preventing said gas from carrying said combustion residues from said cylinder into said tube for deposit therein, and a sealing collar mounted on said operating rod in cooperation with said operating tube for preventing gas from leaking from said operating tube into said receiver.

5. In a machine gun with a barrel having a boreof predetermined diameter with a forward muzzle end and a rearward receiver end having a receiver including mechanism which operates said gun that improvement which consists of:

gas actuating and evacuation means responsive to gas pressure generated by the discharge of a round in said barrel for operating said receiver mechanism and collecting exhausted gas for discharge at a location at least as far forward as adjacent the muzzle end of said barrel, said means comprising barrel gas port means including a gas port in said bore located generally inthe mid-portion of said barrel a gas cylinder mounted on said barrel, said cylinder having a forwardly located gas inlet port communicating with said barrel gas port and closely adjacent thereto for supplying to said cylinder gas under pressure from said barrel and forwardly and rearwardly located gas outlet ports a piston within said cylinder movable between a for ward position in communication with said cylinder gas inlet port to a rearward position in communication with said rearward gas outlet port an operating tube extending between the rear end of said cylinder and said receiver an actuating rod in said tube, said actuating rod extending through the rear wall of said cylinder for actuation by said piston for movement of said rod in said tube independently of said piston to operate said receiver mechanism gas sealing means including cylinder sealing means positioned between said cylinder and said actuating rod for restricting the passage of exhausted gas carrying combustion residues into said operating tube and rod sealing means mounted on said actuating rod and cooperating with said operating tube for preventing exhausted gas from leaking into said receiver and for controlling deposit of said combustion residues within said operating tube and gas evacuation tube means extending forwardly externally of said cylinder generally parallel thereto and to said barrel from said rearwardly located gas outlet port to a location at least as far forward as adjacent the muzzle end of said barrel said gas evacuation tube means communicating with both said rearwardly and said forwardly located cylinder gas outlet ports for discharging said exhausted gas in a forward direction at least as far forward as adjacent the muzzle end of said barrel. 

1. In a machine gun with a barrel having a bore of predetermined diameter with a forward muzzle end and a rearward receiver end having a receiver including mechanism which operates said gun that improvement which consists of: gas actuating and evacuation means responsive to gas pressure generated by the discharge of a round in said barrel for operating said receiver mechanism and collecting exhausted gas for discharge at a location at least as far forward as adjacent the nuzzle end of said barrel, said means comprising barrel gas port means including a gas port in said bore located generally in the mid-portion of said barrel, a gas cylinder mounted on said barrel, said cylinder having a forwardly located gas inlEt port communicating with said barrel gas port for supplying to said cylinder gas under pressure from said barrel and forwardly and rearwardly located gas outlet ports a piston within said cylinder movable between a forward position in communication with said cylinder gas inlet port to a rearward position in communication with said rearward gas outlet port gas evacuation tube means extending forwardly externally of said cylinder generally parallel thereto and to said barrel from said rearwardly located gas outlet port to a location at least as far forward as adjacent the muzzle end of said barrel said gas evacuation tube means communicating with said forwardly and rearwardly located cylinder gas outlet ports for discharging said exhausted gas in a forward direction at least as far forward as adjacent the muzzle end of said barrel.
 1. In a machine gun with a barrel having a bore of predetermined diameter with a forward muzzle end and a rearward receiver end having a receiver including mechanism which operates said gun that improvement which consists of: gas actuating and evacuation means responsive to gas pressure generated by the discharge of a round in said barrel for operating said receiver mechanism and collecting exhausted gas for discharge at a location at least as far forward as adjacent the nuzzle end of said barrel, said means comprising barrel gas port means including a gas port in said bore located generally in the mid-portion of said barrel, a gas cylinder mounted on said barrel, said cylinder having a forwardly located gas inlEt port communicating with said barrel gas port for supplying to said cylinder gas under pressure from said barrel and forwardly and rearwardly located gas outlet ports a piston within said cylinder movable between a forward position in communication with said cylinder gas inlet port to a rearward position in communication with said rearward gas outlet port gas evacuation tube means extending forwardly externally of said cylinder generally parallel thereto and to said barrel from said rearwardly located gas outlet port to a location at least as far forward as adjacent the muzzle end of said barrel said gas evacuation tube means communicating with said forwardly and rearwardly located cylinder gas outlet ports for discharging said exhausted gas in a forward direction at least as far forward as adjacent the muzzle end of said barrel.
 2. In a machine gun with a barrel having a bore of predetermined diameter with a forward muzzle end and a rearward receiver end having a receiver including mechanism which operates said gun that improvement which consists of: gas actuating and evacuation means responsive to gas pressure generated by the discharge of a round in said barrel for operating said receiver mechanism and collecting exhausted gas for discharge in a forward direction, said means comprising: barrel gas port means including a gas port in said bore located generally in the mid-portion of said barrel a gas cylinder mounted on said barrel, said cylinder having a forwardly located gas inlet port communicating with said barrel gas port for supplying to said cylinder gas under pressure from said barrel and a rearwardly located gas outlet port a piston within said cylinder movable between a forward position in communication with said cylinder gas inlet port to a rearward position in communication with said rearward gas outlet port an operating tube extending between the rear end of said cylinder and said receiver an actuating rod in said tube, said actuating rod extending through the rear wall of said cylinder for actuation by said piston for movement of said rod in said tube independently of said piston to operate said receiver mechanism rod sealing means mounted on said actuating rod and cooperating with said operating tube for preventing exhausted gas from leaking into said receiver and for controlling deposit of said combustion residues within said operating tube and gas evacuation means extending from said rearwardly located cylinder gas outlet port for discharging exhausted gas in a forward direction.
 3. In a machine gun as claimed in claim 2, wherein said gas sealing means further includes cylinder sealing means positioned between said cylinder and said actuating rod for restricting the passage of exhausted gas carrying combustion residues into said operating tube.
 4. In a machine gun as claimed in claim 3 wherein said gas seal means consists of an obturating nut positioned between said cylinder and said operating rod tube for preventing said gas from carrying said combustion residues from said cylinder into said tube for deposit therein, and a sealing collar mounted on said operating rod in cooperation with said operating tube for preventing gas from leaking from said operating tube into said receiver. 